In recent years, in view of problems of exhaustion of energy resources, saving in vehicle fuel consumption has been strongly demanded. On the other hand, due to reduction in vehicle prices and so on, vehicle owners have increased to such an extent that there is a trend that each person owns one vehicle. As a result, there has been a problem of wasting energy because, for example, a four-seated vehicle is driven, loaded only with the driver.
Consequently, various studies are being made to downsize vehicles for saving fuel consumption. As a method for saving fuel consumption by downsizing a vehicle, it can be said that the vehicle is the most efficient when it is structured as a two-wheeled vehicle for one person.
As a two-wheeled vehicle for one person as described above, for example, a type of vehicle in which the occupant rides in a standing posture is disclosed in Japanese Patent Application Publication Nos. JP-A-2005-75070 and JP-A-2005-94898. On the other hand, a type of vehicle in which the occupant rides in a seated posture is disclosed in Japanese Patent Application Publication No. JP-A-2005-145296 (Patent Documents 1 to 3).
However, there has been a problem in such vehicles (two-wheeled vehicles for one person) that, when a lateral acceleration (centrifugal force, indicated by an arrow A in FIG. 10B) acts on a vehicle body due to cornering, the inner wheel during cornering is prone to lift (refer to FIG. 10B), leading to insufficient stability during cornering, and thus causing lateral overturning of the vehicle during cornering unless it is sufficiently slowed down.
On the other hand, Japanese Patent Application Publication No. JP-A-2001-55034 describes a technology, though for a four-wheeled vehicle, in which, by making a vehicle body support right and left wheels through pivot transfer levers, and also by connecting together the right and left pivot transfer levers with a connecting rod, a link mechanism is formed by the two pivot transfer levers and the connecting rod together with the vehicle body, and then by driving the link mechanism (pivot transfer levers) with an actuator, the right and left wheels are inclined toward inside of cornering, thus aiming at improving a cornering performance (Patent Document 4).